Johnstown, Colorado 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

882
FXUS65 KBOU 060914
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
314 AM MDT Fri Jun 6 2025

.KEY MESSAGES...

- Strong to severe storms possible this afternoon with hail and
  damaging wind gusts the primary threats.

- Warmer Saturday with few to no showers/thunderstorms.

- Sunday into next week, near normal temperatures with chances for
  showers and storms each day.

&&

.UPDATE...
Issued at 300 AM MDT Fri Jun 6 2025

The signal for strong to severe storms over Elbert and Lincoln
Counties today is robust in the model guidance. A shortwave trough
will be perfectly timed with peak heating this afternoon to
enhance the forcing and instability. Model soundings show healthy
mixed layer CAPE values above 1,000 j/kg with the best forcing
within and just below the hail growth zone. There is agreement
with SPC on the inclusion of an enhanced risk for severe storms
with hail exceeding 2" possible in those two counties. The threat
for severe weather over the I-25 corridor and rest of the
northeast plains will be dependent on instability. If
morning/midday showers end up having good coverage across the
area like in the 06Z NAM Nest solution, then conditions will be
too cool for severe weather elsewhere. However, if the showers
dissipate and more sunshine and instability develops, the I-25
corridor and northeast plains will also see strong to severe
storms with hail up to 2" possible. At this moment, the first
solution where conditions are too stable appears more likely.

&&

.DISCUSSION /Through Thursday/...
Issued at 146 PM MDT Thu Jun 5 2025

Showers and thunderstorms first started forming over the higher
terrain late this morning. Low clouds may have delayed showers and
storms moving off the higher terrain by an hour or two, but
scattered to numerous showers and storms are still on track to for
the urban corridor and eastern plains this afternoon and evening
as a shortwave trough tracks across the region. MLCAPE is up to
1000 J/kg and there`s plenty of moisture and shear to support
strong, to occasionally severe thunderstorms with hail a little
over 1 inch in diameter. Many runs of the HRRR and the last couple
of the NAMNest show a strong/severe storm forming over northern
Weld County and then tracking southeast across Morgan and
Washington Counties through the afternoon hours. This is where the
highest severe weather threat will be. Elsewhere, heavy rain,
small hail (mostly), and wind gusts to 40 mph will be possible
with the stronger storms. The storms come to an end mid to late
evening as the airmass stabilizes and storms move off to the east.
A few light showers will be possible after midnight.

Another shortwave trough is on track to trigger scattered to
numerous showers and thunderstorms Friday. It will remain moist
with dew points in the lower to mid 50s over northeast Colorado.
Similar to today, instability will be marginal for severe
thunderstorms with MLCAPE up to 800 J/kg. The strongest storms are
expected to produce hail up to around 1 inch in diameter and
brief heavy rainfall. The first storms of the day form over the
mountains late in the morning and then spread eastward during the
afternoon hours. Showers and storms progress east of the urban
corridor by early to mid evening and then east of the area by
midnight.

On Saturday, we are still looking for drier northwest flow aloft.
Temperatures will climb into the lower to mid 80s under mostly
sunny skies. We see a cold front push south through the area
during the evening, but with a drier and more stable airmass in
place, do not expect this to produce any showers or thunderstorms.
North to northeast flow behind the front will slowly increase
moisture across the area.

Better moisture and instability will be over the area again
Sunday. This combined with a shortwave embedded in the northwest
flow aloft will bring a round of showers and thunderstorms Sunday
afternoon and early evening. Temperatures cool a little for Sunday
as well with highs across northeast Colorado in the 70s.

For Monday and Tuesday, a weak upper level ridge tracks across
the Great Basin and Central Rockies. This will bring warmer
temperatures with highs returning to the lower to mid 80s across
northeast Colorado by Tuesday. With enough moisture and
instability in place, we expect daily afternoon/evening showers
and thunderstorms. Though coverage may end up a little less than
we`ve seen this week.

The ridging slides east of the area by Wednesday and west-
southwest flow aloft is expected to prevail for Wednesday and
Thursday. Chances for afternoon/evening showers and thunderstorms
continue. Increased coverage of showers/storms will be possible if
we see a more organized shortwave trough. Temperatures look to be
near normal with highs in the lower to mid 80s across northeast
Colorado.

&&

.AVIATION /06Z TAFS through 06Z Saturday/...
Issued at 1158 PM MDT Thu Jun 5 2025

Low clouds will likely persist throughout the night tonight with
ceilings dropping slowly. Ceilings may drop from 3-5 kft down to
500-1,500 feet. A few model solutions show fog developing around
sunrise at all terminals. However, it is more likely that light
mist or drizzle develops than fog. The end of the morning low
ceilings may extend beyond 14-15Z, when the TAFs currently have
the end time. Worst case scenario seems to be that the low clouds
will move out at 17Z. There is a robust signal in the models that
there will be afternoon thunderstorms. The main concern will be
hail and low visibility which could reach as low as 1 SM. In
addition, winds could gust as high as 40 knots in these storms.

There will again be a threat for low clouds and fog Friday night.
However, the most likely solution is that fog does not develop at
all terminals although if fog does develop, it could bring
visibility down to a quarter of a mile.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$

UPDATE...Danielson
DISCUSSION...Meier
AVIATION...Danielson